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Homework Help: Naming Ionic Compounds

  1. Feb 6, 2006 #1
    Why is NO2 called nitrite? I'm going over this again and I'm still confused.

    Part 1: Cations

    Group 1A and 2A cations are given the name of the metal plus the word "ion."

    Example: Mg 2+ is called a "magnesium ion."

    Some metals form more than one kind of cation as we saw in the last section. This is often true of transition metals. To distinguish the different charges of a cation, Roman numerals are added in parentheses to the element name.

    Example: Iron has two possible charges when ionized: Fe 2+ and Fe 3+ . These are named respectively Iron(II) and Iron(III). Notice that there is no space between the name and the left parenthesis.

    Got that...

    Part 2: Anions

    Single-atom anions (nonmetals) are named by replacing the -ine ending of the element with -ide.

    Example: Chlorine becomes Cl - when it ionizes.
    Its name changes from chlor ine to chlor ide.

    ...and that...but this...:confused:

    B. Polyatomic ("many atom") ion names must be memorized. A table of these ions is below. Most of the polyatomic ions are anions. I highly suggest you print this table and keep it handy in your notebook.

    ...can't memorize them if you don't understand them.

    I'm reviewing and this is one of the things I need to relearn as it's obviously causing me a lot of trouble. My text book doesn't seem to have anything on it and that's all that's in the lesson.
  2. jcsd
  3. Feb 6, 2006 #2


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    NO2 is called Nitrogen Dioxide.
    NO2- is the nitrite ion.

    I dont think there is a reason for why the ion has that name (other than the Nitr[/i[] in Nitrogen). You just need to memorize the names of the common polyatomic ions.
  4. Feb 6, 2006 #3
    [itex][NO_3]^-[/itex] = Nitrate
    [itex][NO_2]^-[/itex] = Nitrite
    [itex][SO_4]^{-2}[/itex] = Sulfate
    [itex][SO_3]^{-2}[/itex] = Sulfite

    The polyatomic ion with the most oxygen ends in -ate while the one with the least oxygen ends with -ite. Here is how it works if there are more than two ions in a "group" :

    [itex][ClO_4]^-[/itex] = Hyperchlorate
    [itex][ClO_3]^-[/itex] = Chlorate
    [itex][ClO_2]^-[/itex] = Chlorite
    [itex][ClO]^-[/itex] = Hypochlorite

    Do you catch the general pattern?
    Last edited: Feb 6, 2006
  5. Feb 6, 2006 #4


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    The way I remember it is that the most common polyatomic ends with "ate". One less oxygen is "ite". One less than "ite" is "hypo____ite". One more than most common is "per______ate"

    [itex][ClO]^-[/itex] = Hypochlorite
    [itex][ClO_2]^-[/itex] = Chlorite
    [itex][ClO_3]^-[/itex] = Chlorate
    [itex][ClO_4]^-[/itex] = Perchlorate

    I'm not sure if it's entirely true, but it seems to hold true from what I've seen. Phosphorus tries to form phosphates, sulphur tries to form sulphates, nitrogen tries to form nitrates. Chlorine may be an exception since chlorate is very reactive.
    Last edited: Feb 7, 2006
  6. Feb 7, 2006 #5
    Alright, I'm starting to piece some of this together but I'm still a bit confused...the chart on the lesson page says, copied and pasted here, :

    NO2 - nitrite
    NO3 - nitrate


    NO2 - Nitrogen Dioxide

    What about this? This one is a bit longer than the other ones...

    HSO4 - hydrogen sulfate or bisulfate
  7. Feb 7, 2006 #6
    IT is an ion of sulfuric acid: H2SO4
  8. Feb 7, 2006 #7
    I'm not following, sorry... ^_^
  9. Feb 7, 2006 #8


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    HSO4- is the biSulfate ion, or Hydrogen Sulfate under the new naming system (I am old, so I like the old ways best).
    SO4-2 is the Sulfate ion, so after adding a Hydrogen, it becomes Hydrogen Sulfate with a new charge.

    [Sulfuric acid, H2SO4 dissassociates in water to form H+ and HSO4- ions which will further dissasscociate to form SO4-2 ions and more H+ ions.]
  10. Feb 10, 2006 #9
    The reason for the strange name is that nitrite is a trivial name. Trivial names are names often made up by non-scientists to make it simple to remember its name.

    take [tex]NaCl[/tex] for example. Its trivial name is "salt", "table salt" and so on, while its systematic name is sodium chloride.

    The same goes for [tex]NO_2[/tex]. Its trivial name is nitrite but its systemativ name is nitrogen dioxide.

    It is often easier to remember the systematic name of an ion because it follows the same pattern.

    2 atoms makes di, three makes tri- and so on.
    Last edited: Feb 11, 2006
  11. Feb 10, 2006 #10
    Aw, that is easier...nothing is ever easy anymore...:rolleyes:
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